The present invention relates to the use of computer systems in connection with transactions, such as financial transactions, and particularly to enhance the ability of parties to enter into substantial transactions with increased security.
Computers and communications technology are coming into wide use as aids to commercial transactions. Transactions such as personal check verifications and credit card purchase authorizations have become everyday experiences.
One type of transaction aid that has been proposed is an offline “identity-based” transaction system in which a Certification Authority (CA) vouches for validity and veracity of data in a user's certificate distinguish between two types of public key signature based transaction systems. Systems of this type utilize state-of-the-art techniques such as public keys, private keys and digital signatures. The role of digital signatures is to replace real-life signatures and allow a user in an “electronic world” to have a mechanism for signing documents. The digital signature identifies the signer and unequivocally associates the signer with the document signed. It provides non-repudiation of the sender and enables transitive passing of authenticated messages. The nature of CA's, public keys, private keys and digital signatures is explained in Schneier, Bruce, Applied Cryptography, Second Edition, John Wiley & Sons, Inc. (1996). As used herein, a “user” is a person, or a computer program acting on behalf of a person or a group of persons.
In order to be able to increase the scale of systems that use digital signatures, a mere personal digital signature scheme is not enough. In a crude form, every user must have the “signature verification key” of every other user. Therefore, the notion and architecture of the CA has been suggested. In fact, a CA is an entity that vouches for the correctness of very specific messages, each of which establishes the association of “user identity” with the user's “signature verification key”. Thus, a CA architecture is in fact a bootstrapping of the notion of digital signature. The individual users now do not have to have the verification key of each user, instead they can be presented with a signature and a “certificate” where the CA signs the standard message associating a user with a verification key. To this end there are various schemes, including a standard one, described in CCITT Recommendation X.509, 1989.
In a basic CA-based architecture, a certificate is either “pushed” to the user by the signer, or the certificate is “pulled” from the CA by the user. The “or” is not exclusive due to the possibility of revocation of certificates. In any case, we can assume an established “CA architecture” is in existence. For high scalability, there can be a hierarchy of CA's (CA infrastructure). A user will go up the tree-structure to a CA that it trusts. The structure does not have to be a hierarchy and may have more semantics; namely various CA's may deal with certain tasks, key types and transactions.
Systems of the type described above have proven able to support transactions in which it is sufficient to verify the identity of a party, typically a purchaser. However, they do not appear to be well suited for more complex transactions in which one or both parties are obligated to perform specific acts, or to achieve specific goals, or to possess specific characteristics, or qualifications, or credentials, or to have a certain state, or condition. Applicants have observed that in a commercial environment where financial service support for a transaction is needed, there is much more relevant information associated with a transaction than what a certificate provides. Similar considerations apply to a variety of transactions, such as those in which the qualifications, or credentials, of a party must be assured, health care, etc. While the following description of the invention will relate primarily to financial transactions, such transactions should be understood to represent only one exemplary area where the present invention can be used and the scope of the invention is as defined in the appended claims.